Considerably Unfolded Transthyretin Monomers Preceed and Exchange with Dynamically Structured Amyloid Protofibrils
2015 (English)In: Scientific Reports, ISSN 2045-2322, Vol. 5, no 11443Article in journal (Refereed) Published
Despite numerous studies, a detailed description of the transthyretin (TTR) self-assembly mechanism and fibril structure in TTR amyloidoses remains unresolved. Here, using a combination of primarily small -angle X-ray scattering (SAXS) and hydrogen exchange mass spectrometry (HXMS) analysis, we describe an unexpectedly dynamic TTR protofibril structure which exchanges protomers with highly unfolded monomers in solution. The protofibrils only grow to an approximate final size of 2,900 kDa and a length of 70 nm and a comparative HXMS analysis of native and aggregated samples revealed a much higher average solvent exposure of TTR upon fibrillation. With SAXS, we reveal the continuous presence of a considerably unfolded TTR monomer throughout the fibrillation process, and show that a considerable fraction of the fibrillating protein remains in solution even at a late maturation state. Together, these data reveal that the fibrillar state interchanges with the solution state. Accordingly, we suggest that TTR fibrillation proceeds via addition of considerably unfolded monomers, and the continuous presence of amyloidogenic structures near the protofibril surface offers a plausible explanation for secondary nucleation. We argue that the presence of such dynamic structural equilibria must impact future therapeutic development strategies.
Place, publisher, year, edition, pages
Nature Publishing Group: Open Access Journals - Option C / Nature Publishing Group , 2015. Vol. 5, no 11443
IdentifiersURN: urn:nbn:se:liu:diva-120227DOI: 10.1038/srep11443ISI: 000356857900001PubMedID: 26108284OAI: oai:DiVA.org:liu-120227DiVA: diva2:842642
Funding Agencies|This work was funded by the Danish Council for Independent Research, Medical Sciences; Danish Council for Independent Research, Medical Sciences, Sapere Aude programme; Drug Research Academy; DANSCATT; Swedish Research Council; Linux cluster at University of Copenhagen by the Carlsberg Research Foundation; FTIR spectrophotometer by the Apotekerfonden2015-07-212015-07-202015-11-26